? US Robotics Sportster 28,800 Fax modem - PSU requirements.

I have mislaid the power supply for a US Robotics Sportster 28,800 Fax Modem (with V34 and V32bis) which I would like to use. This modem lights up and *appears* to work with a supply of 9 volts DC, drawing around 200mA, but I'm not yet entirely convinced that it is performing correctly.

I did some Google searching and haven't managed to find a manual or any information about the particular unit that I have, but I did see a similar modem mentioned which requires 9 volt AC to power it. I haven't yet attempted feeding my modem with AC because I don't want to risk damaging it..

Can anyone in this NG tell me what the correct voltage should be, and if it should be AC or DC? Is there anywhere on the 'net where I might find a User Manual for this modem? I've searched for one, so far without any success.

Many thanks,

- Dave.

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David C.Chapman - (dcchapman@minda.co.uk)
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Reply to
David Chapman
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Have you tried contacting a support technician

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Alternatively, search for the 33.6 version manual - which was the same hardware with a firmware update.

Good Luck, Sheila

Reply to
Sheila

I can check when I get home. I have boxes of those things.

Reply to
Cydrome Leader

Only data I have is for US models, but perhaps you'll find something of use here. Since there have been 18.3 gazillion different "sportster" models, it would help if you posted the exact part number.

USR Part Number: Voltage: Model Number(s)

1.015.090-B: (Input 120VAC, 60Hz) (Output: 9.2 vac@533mA): 00021800 00021900 00026100 00026400 00026500 00026501 00026502 00026600 00026601 00026700 00026701 00026702 00026800 00026801 00026802 00026805 00026806 00026900 00026901 00026902 00026905 00027800 00092200

1.015.1202-B: (Input 120VAC, 60Hz) (Output: 20vac @750mA):

00027900 00074500 00074600 00074700 00074800 00083900 00083901 00083902 00084100 00114100 00117200 00126500 00126501 00126502

1.015.1286: (Input 120VAC, 60Hz, 16Watts) (Output 9VAC, 1000mA):

00083903 00083905 00083907 00083908 00083909 00084000 00084001 00084002 00084003 00084004 00084005 00126502 00126504 00126505 00178400 00178600 00178602 00178900 00178902 00564100 00568400 00568600 00568602 00568603 00568900 00568902 00568903

1.015.1443-00: (Input: 120v AC, 60 Hz, 21 watts) (Output: 9 volts AC, 1500 mA):

00560500
Reply to
Mike S.

In message , Mike S. writes

Very many thanks for all of the contributions made in response to my posting.

I have just sent a query to the support technicians at US Robotics and am awaiting a reply.

I'm not sure of the exact model number - printed on the actual case is a number which is similar, but different, to the list of models shown above - it reads 1.020.139-B. There is also a white adhesive label on the underside which says: CJE-0268 followed by the long number

0108390014294363,

From the above information it appears that the unit does require an AC supply, but I'll wait a day or so to see if US Robotics reply before I try experimenting with the supply voltage.

Thanks again - Dave

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David C.Chapman - (dcchapman@minda.co.uk)
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Reply to
David Chapman

If it is fed with AC it'll be to a rectifier and regulator circuit turning it into DC, so be on the safe side and feed it with DC anyway.

Run it on 12v DC, it's likely the regulators will be able to dissipate it if it is excessive voltage.

Steve Terry

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Reply to
Steve Terry

If it needs AC, then it is most likely generating plus and minus dc voltages inside. Since it is a modem, and has rs232, it would need + and - voltages.

If you feed it dc only, you will only have one of the supplies in the unit.

Try a 9 volt ac wart.

Reply to
tm

We (still) use the USR Message Modem and that needs 18Vac. My Googling indicates 9Vac 400mA

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Woody

harrogate three at ntlworld dot com
Reply to
Woody

IIRC the most common type is 13VAC.

Bear in mind that if it connects to the PC via RS232, it must be capable of generating plus and minus 12v rails.

Reply to
ian field

9V AC sounds about right for the Sportster 14400 (very similar). It's definitely an AC supply and I'm fairly sure it's 9V. I think it may be a bit more than 400mA, BICBW.

Theo

Reply to
Theo Markettos

Well yes and no. IMSMC RS232 can start at anything up to +/- 15V but is more usually 12. The important bit is what it is doing when it gets to the other end - ISTR +/-5V absolute minimum, usually 6.

And with electronics from anywhere in the last 30 years or so higher voltages can easily be generated by cap/diode pumps or more specialist chips. It's just that using ac as the source means that they don't need to have an oscillator on board.

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Woody

harrogate three at ntlworld dot com
Reply to
Woody

A 9V AC power supply is sufficient to generate that without resorting to switching; the peak voltages from the supply are

+/- 12.7 volts. A power supply which depends on that is unlikely to function well with a 9V DC wall wart, though.

I don't know, but in real life I've connected a standard RS232 interface to a board header which provided only TTL levels (i.e. 0 and 5V) and had it function. I did this from desperation, though, and wouldn't recommend it.

Dennis Ferguson

Reply to
Dennis Ferguson

I built a board here that runs off 5V. A MAX232 driver/charge pump drives the serial line fine.

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Reply to
Bob Eager

Its the darndest thing tho', I've never yet seen a MAX232 in any of the modems I've had apart.

Reply to
ian field

Should have made it clear, mine wasn't a modem...it was a clone of a PDP-8....!

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Reply to
Bob Eager

In which case - what the hells it got to do with the OP's question.

Reply to
ian field

For what it's worth, I have here a US Robotics 56K Faxmodem, complete with power supply. The label on the latter says "US Robotics SP3a. Input

230v~ plus/minus 10%. Output 9v~ 1000mA"
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John Ray
Reply to
John Ray

It shows that a 5V supply could be sufficient, depending on circuitry. Do keep up.

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Reply to
Bob Eager

an original USR power adapter P/N 1.015.1286 = 9VAC 1000mA

that's the same power adapter for any of the 28.8 and 33.6 modems I have here.

Reply to
Cydrome Leader

In message , Sheila writes

Well, here's the definitive response that I've now received from US Robotics:-

"Based on the FCC number CJE-0268 that you gave us is from the model number USR0839. If you have this model number then the specification of the power supply is 20V AC .5A."

So, the correct voltage WAS somewhere between 9 volts DC and 20 volts AC ;-)

And so to bed! Many thanks to all those who contributed to this posting.

All the best - Dave

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David C.Chapman - (dcchapman@minda.co.uk)
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Reply to
David Chapman

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